Leveling attachment for a fork lift truck



Nov. 28, 1961 c. L. STONE 3,

LEVELING ATTACHMENT FOR A FORK LIFT TRUCK Filed March 1, 1960 3 Sheets-Sheet 1 INVEN TOR.

67/484525 4.. STONE;

7729/7moz mmr m'a Nov. 28, 1961 c. STONE 3,010,595

LEVELING ATTACHMENT FOR A FORK LIFT TRUCK Filed March 1, 1960 3 Sheets-Sheet 2 HIEQIE 47 25 44 J 5 Q 49 I l I l I l'l I l l 23D I l l I Ll M INVENTOR. F76. 4 /5 CO /4.245s L. s TONE,

Nov. 28, 1961 c. L. STONE 3,010,595

LEVELING ATTACHMENT FOR A FORK LIFT TRUCK Filed March 1, 1960 3 Sheets-Sheet 3 47 FIG. 5.

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United States Patent 3,010,595 LEVELING ATTACHMENT FOR A FORK LIFI TRUCK Charles L. Stone, 803 Elmdale, Shreveport, La. Filed Mar. 1, 1960, Ser. No. 12,061 2 Claims. (Cl. 214-701) This invention relates to fork lift trucks, and more particularly to an attachment for leveling the forks of a fork lift truck when the truck is positioned on sloping or irregular terrain.

A main object of the invention is to provide a novel and improved leveling attachment for a fork lift truck, said attachment being simple in construction, being easy to install, and providing a means for enabling a fork lift truck to operate efficiently while on irregular or sloping terrain.

A further object of the invention is to provide an improved leveling attachment for a fork lift truck, which may be either embodied in the original structure of a fork lift truck or may be installed on a fork lift truck of conventional design, the attachment being inexpensive to fabricate, involving only a few parts, and providing a convenient and dependable means for accurately moving the forks of a lift truck equipped with the attachment to a horizontal position to enable loads to be safely and efficiently handled even though the lift truck is located on sloping or irregular terrain.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

FIGURE 1 is a fragmentary perspective view of a fork lift truck provided with an improved leveling attachment constructed in accordance with the present invention.

FIGURE 2 is a front elevational view, to a reduced scale, showing the manner in which the leveling attachment allows a load to be efflciently and safely handled in a horizontal position even though the truck is supported on sloping terrain.

FIGURE 3 is an elevational view of the apron plate assembly and parts associated therewith, as employed in the fork lift truck of FIGURE 1, said view being to a somewhat enlarged scale as compared with FIGURE 1, and being taken substantially on the line 3-3 of FIG- URE 4.

FIGURE 4 is an enlarged horizontal cross sectional view taken substantially on the line 44 of FIGURE 1.

FIGURE 5 is a vertical cross sectional view taken on the line 5-5 of FIGURE 3 but showing a portion of the fork lift truck elevator frame, which is omitted in FIG- URE 3.

FIGURE 6 is an enlarged horizontal cross sectional view taken on the line 66 of FIGURE 3.

FIGURE 7 is an enlarged cross sectional view taken on the line 77 of FIGURE 3.

FIGURE 8 is a cross sectional view taken on the line 8-8 of FIGURE 7.

Referring to the drawings, 11 generally designates a fork lift truck which is provided with a vertical upstanding elevator frame 12 which is hingedly secured to the tmck and in which is slidably engaged the elevator lift frame 13, the lift frame being guided for vertical movement by the telescopic engagement of its vertical side bars 16, 16 in the guide channels 17, 17, forming part of the fixed elevator frame 12. The elevator frame 12 is provided with the vertical hydraulic cylinder 18 in which the piston-operated member 19 is engaged, whereby the lift frame 13 may be elevated by admitting hydraulic fluid under pressure into the cylinder 18. The

admission of the hydraulic fluid, and the discharge thereice of from the cylinder 18 is controlled by conventional valve means, for example, a valve control lever 20 provided in a valve control assembly 21 mounted on the truck adjacent the operators seat 22. The vertical orientation of the frame 12 with respect to a transverse horizontal axis is controlled by conventional means including hydraulic cylinders 23 provided at the sides of the truck and having pistons pivotally connected to the respective sides of the elevator frame 12, the hydraulic cylinders 23 being controlled by a valve having a control lever 24, said valve being part of the control valve assembly 21.

Designated at 25 is the transversely extending vertical apron plate which is slidably engaged with the side channels 16, 16 of the vertical movable lift flame 13, for example,by means of rollers 26 journaled to brackets 27 secured to the rear surface of the apron plate 25, the rollers 26 engaging inside the side channels 16 of the lift frame member 13, as is clearly shown in FIGURE 4. The apron plate 25 is connected to the vertically movable lift frame 13 by chains 28, 28 secured to flange portions 29 of the bracket 27, whereby lifting force is transmitted from the vertically movable frame member 13 to the apron plate 25. As shown in FIGURE 1, the chains 28 may extend over suitable pulleys 3i! rotatably mounted in the top portion of the lift frame member 13 and may be secured to a transversely extending fixed portion 31 of the elevator frame 12, so that the upward force of the vertically movable lift frame 13 will be transmitted through the chains to the apron plate 25.

The structure thus far described is conventional and in itself forms no part of the present invention.

Designated at 32 is a transversely extending vertical face plate which is disposed forwardly adjacent and parallel to the apron plate 25 and which is provided with the forwardly extending fork prongs 33, 33. The face plate 32 is pivotally connected to the apron plate 25 at the upper intermediate portions of said plates by a pivot assembly comprising a pivot shaft member 34 which extends through a horizontal bearing bushing 35 secured to the apron plate 25 at its upper intermediate portion, suitable wear bushing elements 36 and 37 being interposed between the pivot shaft 34 and the main bushing member 35. Said main bushing member 35 is provided with an annular flange 38 which is fastened to the apron plate 25, whereby the sleeve-like bushing member 35 is rigidly secured to said apron plate and extends through an aperture provided in the upper interme diate portion of the face plate 32. The pivot shaft 34 extends through the wear bushings 36 and 37 and is provided at its inner end with suitable retaining means, for example, a cotter pin 39 which extends through the end of the shaft 34 and which cooperates with a Washer 40 surrounding the shaft and disposed between the cotter pin 39 and the flanged outer portion of the wear bushing 37. At its forward end, the pivot shaft 34 is provided with a flange 41, the flange being secured to the face plate 32 by a fastening screw 42, as shown in FIGURE 5, whereby the pivot shaft 34 is rigid with the face plate 32.

The prongs 33 are adjustably secured to the face plate 32, said prongs being provided at the top ends of their vertical supporting portions 43 vw'th hook-like flanges 44 which are engaged over the serrated top edge 45 of the face plate 32. Cooperating lugs 45 are provided at the lower portions of the vertical members 43, and clamping screws 47 are threadedly engaged vertically through the hook-like flanges 44. The lugs 46 engage the bottom edges of the face plate 32 and the clamping screws 47 exert clamping pressure on the top edge of the face plate opposing the lugs 46, whereby to rigidly clamp the prongs 33 to the face plate.

The clamping screws 47 are adapted to engage in the notches defined between selected pairs of serrations in the top edge of the face plate, so that the prongs will be locked against lateral movement when the clamping screws 47 are tightened.

A U-shaped bracket member 48 is secured to the intermediate portion of the bottom margin of the face plate 32 and receives the bottom marginal portion of the apron plate 25, as is clearly shown in FIGURE 5, the bracket member 43 being of sufficient height to allow a substantial amount of rotary movement of the face plate 32 with respect to the apron plate 25 around the axis of the pivot bolt 34. Generally U-shaped horizontal brackets 49, 49 are secured to the upper portions of the side margins of face plate 45 and extend around the side edges of the apron plate 25, respective bearing rollers 5t 5% being journaled on the ends of the rear arms of the U-shaped brackets 42, the rollers 5t engaging the rear surface of the apron plate 25 at the upper side marginal portions thereof, whereby to transmit load forces from the prongs 33 to the upper side portions of the apron plate 25. A pair of additional bearing rollers 51, 51 are jou-rnaled in the lower side portions of the apron plate 25 on axes inclined upwardly and inwardly, as shown in FIGURE 3, the bearing rollers 51 engaging the rear surface of the face plate 32 and cooperating with the rollers 50, St! to transmit load forces from the face plate 32 to the apron plate 25. Angular adjustment of the face plate 32 around the axis defined by the pivot bolt 34 is facilitated because of the upward and inward inclination of the axes of the bearing rollers 51, 51, even when the prongs 33 are supporting a substantial load.

As will be apparent from FIGURE 3, the axes of the bearing rollers 51 are located substantially radially with respect to the pivotal axis defined by the pivot bolt 34, to facilitate rotation under load of the face plate 32 around the pivotal axis defined by pivot bolt 34.

As shown in FIGURE 4, the U-shaped horizontal bracket members 49, 49 are of sufficient length to provide substantial clearance for rotation of the face plate 32 with respect to the apron plate 25 around the axis of the pivot bolt 34.

A hydraulic cylinder 60 ispivotally connected at one end thereof, as shown at 61, to the top portion of an upstanding lug 62 provided on the top edge of the apron plate 25. The outer end of the piston rod 63 associated with the hydraulic cylinder 6% is pivotally connected at 64 to the top end of an upstanding lug 65 provided on the top edge of the face plate 32, the cylinder 60 being arranged substantially horizontally and being operated selectively, namely, to move the piston rod 63 in either direction, by hydraulic fluid admitted into the respective end portions of the cylinder through flexible conduits 65 and 67. The direction of flow of the hydraulic fluid under pressure in the conduits 66 and 67 is controlled by a suitable. control valve provided in the valve assembly 21 and having a control lever 68 which is readily accessible to the o orator of the truck. The control valve is arranged to simultaneously admit hydraulic fluid into one of the conduits 66 or 67 and to allow fluid to discharge from the cylinder 60 through the other conduit to the fluid reservoir. By operating the valve lever 63 the direction of the control fluid may be reversed. Thus, in one active position of the control lever 68 the piston rod 63 is extended from the cylinder 69, whereas in another active position of the lever the piston rod 63 is retracted into the cylinder 60. A neutral position is provided wherein the piston rod 63 is locked relative to the cylinder 66.

The conduits 66 and 67 are supported on and secured to the apron plate 25 by suitable clamping and guide brackets, such as the bracket members 7t and 71, and connect to flexible portions 72 and 73 which extend over suitable guide pulleys 74 and 75 journaled in the top portion of the vertically movable lift frame member 13, the flexible conduit portions 72 and 73 having sufiicient slack to allow for the vertical movement of the apron plate 25 produced by the elevation and lowering of the lift frame 13.

As will be readily apparent from the above description, the operator may adjust the inclination of the face plate 32 around the horizontal longitudinal axis defined by the pivot bolt 34 in accordance with the slope or irregularity of the terrain on which the truck is positioned, so that the fork elements 33 will support the load, for example, the load shown in dotted View at 80 in FIGURE 2, in a substantially horizontal position. When the truck moves from one slope to another, the operator is enabled to correspondingly adjust the angular position of the face: plate 32 by suitably manipulating the control lever 63. Thus, the load can be safely and efiiciently handled regardless of the slope or inclination of the terrain on which the truck is positioned, and the load may be maintained in a substantially horizontal position at all times, regardless of changes in the slope or nature of the irregularity of the terrain on which the truck is employed.

As shown in detail in FIGURE 6, the upper bearing rollers are journaled on pivot bolts 82 which are threadedly engaged in the ends of the thickened rear arms. 83 of the horizontal, generally U-shaped brackets 49.. The forward arms of the brackets 49 are secured to the rear surface of the face plate 32 by suitable fastening bolts 84.

The bearing rollers 51, shown in detail in FIGURES 7 and 8, are journaled in opposing pairs of U-shaped bearing bracket members 86, 86 secured to the opposite surfaces of the apron plate 25 adjacent and parallel to the respective inclined rectangular slots 87 formed in the apron plate 25 to receive the bearing rollers 51. Said bearing rollers 51 are provided with oppositely projecting shank portions 88 which are rotatably received between the opposing pairs of bearing brackets 86, 86, thus rotatably supporting the bearing rollers on axes which are arranged radially with respect to the horizontal longitudinal axis defined by the main pivot'bolt 34. Thus, the rectangular slots 87 are arranged perpendicular to the radial axes of the bearing rollers 51.

It should be noted that in certain designs of fork lift trucks the face plate comprises a pair of segments rather than a single plate member. The pair of segments are united in any suitable manner so as to define a unitary face plate assembly. Under these conditions, the invention would be equally applicable, since the pivot bolt assembly including the pivot bolt 34 and the associated parts would be located at the upper intermediate portion of the top face plate segment.

While a specific embodiment of an improved fork lift truck leveling attachment has been disclosed in theforegoing description, it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore, it is intended that no limitations be placed on the inve'htion except as defined by the scope of the appended claims.

What is claimed is:

1. In a fork lift truck of the character described, a vertical upstanding elevator frame, a transversely extending vertical apron plate slidably engaged with said elevator frame, means to elevate said apron plate vertically along said elevator frame, a transversely extending vertical face plate disposed forwardly adjacent and parallel to said apron plate, said face plate being provided with forwardly extending fork prongs, a pivot bolt extending horizontally through said face plate and apron plate, perpendicularly thereto and pivotally connecting said face plate to said apron plate at the upper intermediate portions of said plates, horizontally spaced respective upstanding lug elements rigidly secured to the top edges of said plates, horizontally extensible fluid pres sure operated means connected directly between said lug elements and being constructed and arranged to rotate said face plate relative to the apron, plate, respective bearing rollers journaled in the lower side portions of the apron plate and engaging the face plate in bearing relationship thereto, respective bracket members secured to the side margins of the face plate and extending around the side edges of the apron plate, and bearing rollers journaled on said bracket members and engaging the rear surface of the apron plate in bearing relationship thereto.

2. In a fork lift truck of the character described, a vertical upstanding elevator frame, a transversely extending vertical apron plate slidably engaged with said elevator frame, means to elevate said apron plate vertically along said elevator frame, a transversely extending vertical face plate disposed forwardly adjacent and parallel to said apron plate, said face plate being provided with forwardly extending fork prongs, a pivot bolt extending horizontally through said face plate and apron plate, perpendicularly thereto and pivotally connecting said face plate to said apron plate at the upper intermediate portions of said plates, horizontally spaced respective upstanding lug elements rigidly secured to the top edges of said plates, horizontally extensible fluid pressure operated means connected directly between said lug elements and being constructed and arranged to rotate said face plate relative to the apron plate, respective bearing rollers journaled on upwardly and inwardly inclined axes in the lower side portions of the apron plate and engaging the face plate in bearing relationship thereto, respective bracket members secured to the upper portions of the side margins of the face plate and extending around the side edges of the apron plate, and bearing rollers journaled on horizontal transverse axes on said bracket members and engaging the rear surface of the apron plate in bearing relationshp thereto.

References Cited in the file of this patent UNITED STATES PATENTS 2,468,326 Gleason Apr. 26, 1949 2,690,272 Quayle Sept. 28, 1954 20 2,720,993 Hull Oct. 18, 1955 

